Robert Jansen
Technical Sales Manager
Retaining structures along railway lines place additional demands on anchors. Return currents, cathodic protection, and stray currents require an electrically insulated anchor. Deepro is the only company in Europe to supply an ETA-certified, electrically insulated strand anchor in PL3 class.
Rail anchors secure earth-retaining structures that lie directly on or in the immediate vicinity of railway tracks. These include quay walls along tracks in port areas, construction pits for stations and underpasses, retaining walls along rail embankments, and sheet piles for track infrastructure.
The wall absorbs and transfers ground pressure and water pressure. For greater retaining heights or more stringent deformation requirements, the wall is anchored. The anchor transfers the horizontal tensile forces to a stable soil layer behind the slip surface. Strand anchors are an efficient solution for this: high anchor force, slim profile, and suitable for execution in a confined workspace next to an active track.
With rail, an extra dimension comes into play: the anchor system must not form an electrically conductive connection with the track structure or nearby underground pipes. An electrically insulated strand anchor (PL3) interrupts this path and prevents corrosion or unwanted current discharge due to return currents and cathodic protection. Additionally, prestressing steel in a railway environment must demonstrably be resistant to stress corrosion cracking and hydrogen embrittlement – degradation mechanisms that occur precisely in highly loaded, conductive structures.
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In the design and implementation of anchors in railway projects, alongside the usual geotechnical boundary conditions, there are also requirements from the asset manager and the licensing authority. These affect both the structural design and the execution during possession periods:
Bridges have long preparation and approval processes. Early alignment between the constructor, contractor, operator, and anchor supplier prevents delays in design approval and ensures both safety and the schedule around commissioning.
An anchored earth-retaining structure alongside a railway consists of a wall, a waler, and an anchoring system that transfers the horizontal forces into the ground.
The wall is usually a diaphragm wall or combi-wall. The wall absorbs ground pressure, water pressure, and overhead loads from the track and surroundings, and transfers these through bending and clamping at the base.
The purlin or distribution beam is placed at or just below ground level. This distributes the concentrated anchor forces evenly over the wall and prevents local deformations at the anchor head.
The electrically insulated strand anchor consists of an anchor head with wedges, a free length in a sheathing tube and an anchored length that transmits force to the subsoil via grouting. HDPE insulation components in and around the anchor head prevent electrical contact between the prestressing steel and the wall or purlin. This interrupts the path for return currents or stray currents.
The rod, purlin, anchor head, and anchored length function as a single system that is both mechanically and electrically attuned to the railway environment.
Every situation is different. In a consultation, we will clearly outline your project and possibilities. You will immediately know where you stand.
Robert Jansen
Technical Sales Manager
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Track uses return currents via the rails. With direct current traction and with cathodic protection of nearby pipelines, stray currents arise that run through conductive paths into the soil. A metallic path via an anchor can then cause undesirable corrosion or current discharge. An electrically insulated anchor (PL3) interrupts this path.
In a PL3 anchor, the prestressing steel is completely separated from the anchor head, anchor plate and purlin by HDPE insulation components. This means there is no conductive connection between the strand and the earth-retaining structure. Deepro is currently the only company in Europe to supply this with ETA certification.
Yes. Stress corrosion and hydrogen embrittlement are the two key degradation mechanisms for prestressing steel under sustained load, particularly in conductive environments such as alongside railway tracks. The steel used complies with EN 10138 and, in combination with a multi-layer PE sheathing, anti-corrosion compound and (for PL3) complete electrical insulation, is demonstrably resistant to both mechanisms. Suitability is guaranteed via the ETA at system level, not for individual components.
For all earth-retaining structures in or near the track area, including sheet piles and combi-walls along tracks, quay walls with track-related loads, construction pits for stations and underpasses, and retaining walls along track slopes. The application follows the requirements of the asset owner and the specific location.
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